Abuse esBuffer to track the vid/aud stream id

This is a bit hacky, but the struct in question sits in PSP RAM.  Better would be to decode the packets manually, but that's a bigger change.

~~Might help~~ Fixes #6275, which is the general goal of this change.  Seems like if there's multiple streams, you get the aus for both but ignore them (can/must, not sure...)  So this defers switching the stream to the decode.

-[Unknown]